Add compileSampleStats

dev/demux.html

@@ -49,6 +49,10 @@
 		const videoTrack = await input.getPrimaryVideoTrack();
 		const drain = new Metamuxer.EncodedVideoSampleDrain(videoTrack);
 
+		console.log(await videoTrack.computeSampleStats())
+		document.body.textContent = performance.now() - start;
+		return;
+
 		const decoderConfig = await videoTrack.getDecoderConfig();
 		const sampleSource = new Metamuxer.EncodedVideoSampleSource(await videoTrack.getCodec());
 		output.addVideoTrack(sampleSource);
@@ -65,7 +69,7 @@
 		}
 		
 		await output.finalize();
-		document.body.textContent = performance.now() - start;
+		
 
 		console.log(target)
 

src/index.ts

@@ -58,7 +58,7 @@ export {
 	WEBM,
 } from './input-format';
 export { Input, InputOptions } from './input';
-export { InputTrack, InputVideoTrack, InputAudioTrack } from './input-track';
+export { InputTrack, InputVideoTrack, InputAudioTrack, SampleStats } from './input-track';
 export {
 	EncodedVideoSample,
 	EncodedAudioSample,

src/input-track.ts

@@ -1,10 +1,11 @@
 import { AudioCodec, MediaCodec, VideoCodec } from './codec';
-import { SampleRetrievalOptions } from './media-drain';
+import { EncodedAudioSampleDrain, EncodedVideoSampleDrain, SampleRetrievalOptions } from './media-drain';
 import { Rotation } from './misc';
 import { EncodedAudioSample, EncodedVideoSample } from './sample';
 
 export interface InputTrackBacking {
 	getCodec(): Promise<MediaCodec | null>;
+	getFirstTimestamp(): Promise<number>;
 	computeDuration(): Promise<number>;
 }
 
@@ -30,6 +31,10 @@ export abstract class InputTrack {
 		return this instanceof InputAudioTrack;
 	}
 
+	getFirstTimestamp() {
+		return this._backing.getFirstTimestamp();
+	}
+
 	computeDuration() {
 		return this._backing.computeDuration();
 	}
@@ -109,6 +114,10 @@ export class InputVideoTrack extends InputTrack {
 			return false;
 		}
 	}
+
+	computeSampleStats() {
+		return computeSampleStats(new EncodedVideoSampleDrain(this));
+	}
 }
 
 export interface InputAudioTrackBacking extends InputTrackBacking {
@@ -174,4 +183,36 @@ export class InputAudioTrack extends InputTrack {
 			return false;
 		}
 	}
+
+	computeSampleStats() {
+		return computeSampleStats(new EncodedAudioSampleDrain(this));
+	}
 }
+
+/** @public */
+export type SampleStats = {
+	sampleCount: number;
+	averageSampleRate: number;
+	averageBitrate: number;
+};
+
+const computeSampleStats = async (drain: EncodedVideoSampleDrain | EncodedAudioSampleDrain): Promise<SampleStats> => {
+	let startTimestamp = Infinity;
+	let endTimestamp = -Infinity;
+	let sampleCount = 0;
+	let totalSampleBytes = 0;
+
+	for await (const sample of drain.samples(undefined, undefined, { metadataOnly: true })) {
+		startTimestamp = Math.min(startTimestamp, sample.timestamp);
+		endTimestamp = Math.max(endTimestamp, sample.timestamp + sample.duration);
+
+		sampleCount++;
+		totalSampleBytes += sample.byteLength;
+	}
+
+	return {
+		sampleCount,
+		averageSampleRate: sampleCount ? Math.fround(sampleCount / (endTimestamp - startTimestamp)) : 0,
+		averageBitrate: sampleCount ? Math.fround(8 * totalSampleBytes / (endTimestamp - startTimestamp)) : 0,
+	};
+};

src/isobmff/isobmff-demuxer.ts

@@ -1673,6 +1673,11 @@ abstract class IsobmffTrackBacking<
 		throw new Error('Not implemented on base class.');
 	}
 
+	async getFirstTimestamp() {
+		const firstSample = await this.getFirstSample({ metadataOnly: true });
+		return firstSample?.timestamp ?? 0;
+	}
+
 	async computeDuration() {
 		const lastSample = await this.getSample(Infinity, { metadataOnly: true });
 		return (lastSample?.timestamp ?? 0) + (lastSample?.duration ?? 0);

todo.txt

@@ -2,8 +2,8 @@
 - Throw if edit list detected
 - Add the new audio codecs to muxers
 - Mov muxer!!! Only mov can hold PCM audio, MP4 cannot
-- Metadata methods for computing average fps and bitrate
 - A stream source?? Or like a callback-driven source
 - onRead callback for Source
 - onHeader, etc callbacks for Matroska
-- Add cslg box
+- Add cslg box
+- https://github.com/Vanilagy/mp4-muxer/issues/83 tell him it's possible now